[Asterisk-Users] Modem Calls

[Steve Underwood]

Scott Nelson wrote:

>My office is investigating using an Asterisk PBX and also going to a VOIP 
>provider for our main phone connections, but one of the tricky things is that 
>we need to have outbound and inbound modem calls (fax too).
>
>I see a lot of talk about faxes but no mention of modems on this list.  I get 
>the impression that modems will be a problem for us.  Is that true?
>  
>
Unless a number of conditions are met, modems above 1200bps over IP are 
somewhere between quirky and non-functional. You won't get anywhere 
unless you use an a-law or u-law codec. Even then, timing issues and 
data slips can cause much trouble. Successful FoIP usually converts the 
modem audio to data, and sends that over the IP channel. The T.38 spec 
supports this. I don't know of a similar spec for other modem uses.

Regards,
Steve